The increasing demand for flexible use of the radio spectrum for emerging new services and applications is the motivation behind numerous research activities worldwide. Efficient access to radio spectrum resources will generate new sources of revenues for worldwide vendors and wireless network operators. Recent studies worldwide indicate that while some systems and mobile operators are starving for more efficient utilization of spectrum resources, most of the radio spectrum resources remain underutilized or unused most of times. The new design of wireless radio infrastructure outlines the new attempts to share the spectrum in a fundamentally novel fashion which would ultimately lead to better utilization of spectrum. The proposed spectrum management architectures and the spectrum sharing functionalities developed recently will result in reducing the time required to tailor a new service to an operator network. Furthermore, the flexible spectrum access and usage leads to more capable and faster services with high Quality of Service (QoS) giving more user satisfaction than conventional networks.
FIG. 1 shows a proposed architecture in a potential scenario where different radio access networks (RANs) are engaged in so-called long-term and short-term spectrum assignment processes. The central diagram of FIG. 1 shows three gateways GW of respective radio access networks RAN1-3 taking part in a LT spectrum negotiation, while the individual base stations of the three RANs 1-3 take part in ST spectrum negotiations. The two graphs to the left of FIG. 1 represent the amount of spectrum allocated respectively to the first base station BS1 of the first radio access network RAN1 and to the second base station BS2 of the second radio access network RAN2. As can be seen in each of the graphs, the low-frequency curve represents the amount of spectrum allocated to the respective base station as a result of LT spectrum negotiations, while the high-frequency curve represents the amount of spectrum as a result of ongoing ST spectrum negotiations. The diagram to the right of FIG. 1 shows the spectrum boundaries set by LT spectrum assignment being adjusted by ST spectrum assignment, in this case with BS3 of RAN3 borrowing a chunk of spectrum from BS2 of RAN2 in the ST spectrum assignment process.
FIG. 2 shows a novel system for spectrum sharing and coexistence. The possibility of spectrum exchange between two or more RANs has been proposed and may ultimately lead to a better utilization of spectrum for wireless mobile networks. In FIG. 2, base stations negotiate over the air during ST spectrum assignments, and may take part in horizontal sharing (a type of sharing in which there is no priority among RANs) while gateways negotiate over an external IP network during LT spectrum assignments, and may take part in vertical sharing (a type of sharing in which one RAN has priority over other RANs). The gateways communicate with a central database, which includes information regarding spectrum policies and regulations, and may also include historical logs of spectrum access and assignments.
The basic idea is to let independent radio access networks (RANs) use the spectrum of other RANs when it is not needed by those RANs. The RANs may negotiate using proposed gateways (GWs).
Four stages for the spectrum negotiations and management have been proposed:
Spectrum Co-existence and Sharing
In the first stage, RANs (perhaps belong to different operators) decide on the size of a shared spectrum band which might be available from one of those RANs beyond their existing dedicated spectrum band. A typical scenario is shown in FIG. 3, in which a dedicated band licensed to RAN1-3 is extended by borrowing extra shared bandwidth. The decision on the precise final boundaries of spectrum is location-dependent and also depends on the nature of the area, e.g. metropolitan area, local area and the coordinates (X,Y) of the RANs and is based on the trade-off between spatial separation and frequency separation. FIG. 4 illustrates a typical scenario for a cellular configuration, including three adjacent cells. It can be observed in FIG. 4 that the initial boundaries of available spectrum are different on a cell-by-cell basis.
Long Term (LT) Spectrum Assignment
In the second stage, after making the decision about the boundaries of spectrum, a negotiation occurs on a couple of minutes' basis through negotiations between gateways assigned to different RANs (i.e. from the different operators) to rearrange the available spectrum to maximize the utilization of spectrum, say between a primary and a secondary system. The idea is to give the capability to each mobile operator to trade its unused spectrum in order to maximize revenue and to provide a new extra source of spectrum when needed to improve the QoS. As depicted in FIG. 5, the spectrum boundaries and guard bands are changed on a couple of minutes basis depending on traffic conditions, the assigned and agreed policy and regulations.
Short Term (ST) Spectrum Assignment
In the third stage, after making the decision about the boundaries of spectrum, a negotiation occurs on a one second or couple of second basis locally between the base stations as depicted in FIG. 1. A typical scenario is depicted in FIG. 6 where a base station from a Metropolitan Area (MA) Deployment has managed to progressively negotiate and get spectrum from a Wide Area (WA) deployment.
Channel Allocation/Radio Resource Partitioning
We assume that, in both the physical layer and the network layer, the radio specifications can be changed in order to provide an acceptable level of BER. At the network level, the interference can be minimised by applying channel allocation/radio resource partitioning (i.e. by suitable selection of channel frequency). After a decision is reached regarding ST Spectrum Assignment, a decision is made on a couple of 10 ms basis to allocate suitable sub-channels to each cell or base station. This is depicted in FIGS. 7A and 7B. Channel allocation also can be applied at the base station (BS) level where the BS decides how to allocate the sub-channels to user equipment (UEs) (perhaps using another smaller sub-channel arrangement).
FIG. 8 shows the hierarchy of the four stages of spectrum assignment based on the employed time granularity. Spectrum Co-existence and Sharing operates on a timescale of hours or a couple of days. LT Spectrum Assignment operates on a timescale of a minute or a couple of minutes. ST Spectrum Assignment operates on a timescale of a second or a couple of seconds. Channel Allocation/Radio Resource Partitioning operates on a timescale of 10 ms or a couple of 10 ms.